U.S. patent number 4,158,917 [Application Number 05/871,830] was granted by the patent office on 1979-06-26 for apparatus for checking the dimensions of mechanical workpieces in movement.
This patent grant is currently assigned to Finike Italiana Marposs, S.p.A.. Invention is credited to Antonio Tagliavini.
United States Patent |
4,158,917 |
Tagliavini |
June 26, 1979 |
Apparatus for checking the dimensions of mechanical workpieces in
movement
Abstract
An apparatus for checking the dimensions of mechanical
workpieces in movement with respect to the apparatus, including at
least one feeler adapted to cooperate with the surface of the
workpiece, or workpieces, at least one transducer connected to the
feeler for providing a signal responsive to the dimensions,
processing apparatus connected to the transducer for processing the
signal and providing a measurement signal, the processing apparatus
including a limiter circuit adapted to receive the signal
responsive to the dimensions and limit it as to variations in a
pre-established direction, providing a relative output signal,
output apparatus connected to the processing means to receive and
utilize the measurement signal and control apparatus. The
processing apparatus include a further limiter circuit, adapted to
receive the output signal of the first limiter circuit and carry
out limitations regarding even variations in the opposite direction
to the pre-established one, the resultant signal being utilized to
obtain the measurement signal. The control apparatus enables and
inhibits the further limiter circuit.
Inventors: |
Tagliavini; Antonio (Bologna,
IT) |
Assignee: |
Finike Italiana Marposs, S.p.A.
(Bentivoglio, IT)
|
Family
ID: |
11104949 |
Appl.
No.: |
05/871,830 |
Filed: |
January 24, 1978 |
Foreign Application Priority Data
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Jan 27, 1977 [IT] |
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3322 A/77 |
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Current U.S.
Class: |
33/501.03;
33/561 |
Current CPC
Class: |
G01B
7/06 (20130101); G01B 7/00 (20130101) |
Current International
Class: |
G01B
7/06 (20060101); G01B 7/00 (20060101); G01B
7/02 (20060101); G01B 007/04 () |
Field of
Search: |
;33/147L,143L,147N,174L,172E,178E,148H |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Electronic Design 19, Sep. 13, 1976, Article--"Use Slew-Rate
Filtering", by M. J. Wright, pp. 110-112, Hayden Publishing Co.,
Inc., Rochelle Park, N. J..
|
Primary Examiner: Aegerter; Richard E.
Assistant Examiner: Little; Willis
Attorney, Agent or Firm: Stevens, Davis, Miller &
Mosher
Claims
What is claimed is:
1. An apparatus for checking the dimensions of mechanical
workpieces in movement with respect to the apparatus,
including:
feeler means adapted to cooperate with the surface of the workpiece
or workpieces;
transducer means coupled to the feeler means for providing a signal
responsive to said dimensions;
processing means connected to the transducer means for processing
the signal responsive to dimensions and providing a measurement
signal; and
output means for receiving and utilizing said measurement signal,
wherein the processing means include:
a first limiter circuit adapted to limit the signal responsive to
dimensions as to variations in a pre-established direction;
a second limiter circuit adapted to limit the signal responsive to
dimensions as to variations in the opposite direction to said
pre-established direction, the first and the second limiter circuit
providing a limited signal;
a filter circuit receiving the limited signal and providing the
measurement signal; and
control means including comparator means connected to the
transducer means and to the filter circuit for providing control
signals depending on the value of the signal responsive to
dimensions with respect to the value of the measurement signal, and
switch means operated by the control signals for selectively
enabling and inhibiting the first and second limiter circuit.
2. The apparatus according to claim 1, for the measurement of
workpieces with interrupted surface, wherein said feeler means
include at least a feeler adapter to contact said surface, the
comparator means including a comparator comparing the signal
responsive to dimensions and the measurement signal, the comparator
providing an output signal of ON-OFF type, one of the values of the
comparator output signal being adapted to control the switch means
for enabling the first limiter circuit--thereby to limit the signal
responsive to dimensions as to its variation speed when said feeler
no longer contacts the surface to be checked due to interruptions
on the workpiece surface--and for inhibiting the second limiter
circuit, the other value of the comparator output signal being
adapted to control the switch means for inhibiting the first
limiter circuit and for enabling the second limiter circuit,
thereby to limit the signal responsive to dimensions during the
transient following the resumption of contact between the feeler
and the workpiece surface, after the interruption has passed.
3. The apparatus according to claim 2, wherein the second limiter
circuit includes an attenuation circuit adapted to receive said
signal responsive to dimensions and said measurement signal for
attenuating according to a pre-set coefficient the difference
signal of the received signals.
4. The apparatus according to claim 2, wherein the second limiter
circuit includes a feedback network adapted to connect the output
of the transducer means and the output of the filter circuit, said
feedback network including a setting circuit for setting a
reference signal for limiting the difference signal of the signal
responsive to dimensions and of the measurement signal according to
said reference signal.
5. An apparatus for checking the dimensions of mechanical
workpieces in movement with respect to the apparatus including
feeler means adapted to cooperate with the surface of the
workpiece, or workpieces, transducer means connected to the feeler
means for providing a signal responsive to said dimensions, process
means connected to said transducer means for processing said signal
and providing a measurement signal, and output means connected to
the processing means to receive and utilize said measurement
signal, wherein the processing means include a first limiter
circuit adapted to receive the signal responsive to the dimensions
and limit it as to variations in a pre-established direction; a low
pass filter connected to the first limiter circuit for providing at
its output said measurement signal; a second limiter circuit
including a feedback network adapted to be connected between the
output of the low pass filter and the input of the first limiter
circuit, for providing to the input of the first limiter circuit
the difference between the measurement signal and the signal
responsive to the dimensions, attenuated according to a constant
co-efficient; and control means including a comparator and switch
means, the comparator having a first input connected to said
transducer means and a second input connected to the output of said
filter, the switching means including a first switch adapted to
connect said feedback network and a second switch adapted to
inhibit the first limiter circuit, the comparator being adapted to
supply a switching control signal to said switching means when the
difference between the comparator input signals takes a determined
polarity.
6. An apparatus for checking the dimensions of mechanical
workpieces in movement with respect to the apparatus including
feeler means adapted to cooperate with the surface of the
workpiece, or workpieces; transducer means connected to the feeler
means for providing a signal responsive to said dimensions;
processing means connected to said transducer means for processing
said signal and providing a measurement signal; and output means
connected to the processing means to receive and utilize said
measurement signal, wherein the processing means include: a first
limiter circuit adapted to receive the signal responsive to the
dimensions and limit it as to variations in a pre-established
direction; a low pass filter connected to the first limiter circuit
for providing at its output said measurement signal; a second
limiter circuit including a summing circuit having a first input
connected to the output of the low pass filter, a second input
adapted for receiving a pre-established reference and an output
adapted for providing a sum signal of the two input signals, the
output of the summing circuit being connectable to the input of the
first limiter circuit; and control means including comparator means
and switching means, the comparator means being connected to the
transducer means and to the output of said filter, the switching
means including a first switch suitable for connecting the summing
circuit to the first limiter circuit input and a second switch
suitable for inhibiting the first limiter circuit, the comparator
means being adapted to provide switching control signals to said
switching means according to the values of said signal responsive
to the dimensions and to the measurement signal.
7. The apparatus according to claim 6, wherein said comparator
means include a first comparator having an input connected to the
transducer means and another input connected to the output of said
filter, the comparator being adapted to supply a switching control
signal to said second switch when the difference between the two
input signals of the comparator undertakes a determined
polarity.
8. The apparatus according to claim 7, wherein said comparator
means include a second comparator having an input connected to the
transducer means and another input connected to the output of the
summing circuit, the second comparator being adapted to provide a
switching control signal to said first switch when the difference
between the input signals of the comparator undertakes a determined
polarity.
Description
The present invention relates to an apparatus for checking the
dimensions of mechanical workpieces in movement with respect to the
apparatus, including feeler means adapted to cooperate with the
surface of the workpiece, or workpieces, transducer means connected
to the feeler means for providing a signal responsive to the
dimensions, processing means connected to the transducer means for
processing the signal and providing a measurement signal, the
processing means including a limiter circuit adapted to receive the
signal responsive to the dimensions and limit is as to variations
in a pre-established direction, providing a relevant output signal,
and output means connected to the processing means to receive and
utilize the measurement signal. More particularly the invention
relates to the comparative measurement of the dimensions of
mechanical workpieces with interrupted surfaces, for example
grooved workpieces, while being machined by tooling machines, such
as grinding machines. Various types of comparator gauges usable for
the described application are already known. Generally these gauges
include one or two adjustable arms carrying feelers, elastic means
urging the feelers towards the workpiece, or workpieces,
transducers adapted to provide signals responsive to the position
of the feelers and electric processing and indication circuits.
Hydraulic dampers are also used to dampen the fall of the feelers
in the workpiece interruptions, or in the spaces separating one
workpiece from the following (e.g., when machining on surface
grinding machines) but keep them in contact with the surfaces to be
gauged.
The electric circuits include circuits for decreasing the variation
speed of the measurement signals in one or in both directions, max.
or min., or averaging circuits.
Generally the indication of known gauges depends in a considerable
way on the operating conditions, in particular the indication
varies as static operation is changed to dynamic operation
(workpiece in movement).
Therefore it is necessary to set to zero the gauges in dynamic
conditions and maintain constant the operating conditions as far as
possible.
An object of the invention is to provide a gauge whose operation
basically does not alter when switching from static to dynamic
workpiece measurement taking, and that will not be affected by
changes in workpiece speed nor by other variations of the working
parameters and working conditions.
A further object of the invention is to provide a gauge that will
work at a high level of accuracy and repeatability even in
particularly unfavorable measuring conditions, due to, for example,
the irregular shape of workpieces, severe working parameters, or
the possible need to use gauges with mechanical characteristics
unsuitable for the measurement of workpieces with interrupted
surface.
These and other objects and advantages are obtained through an
apparatus of the type stated at the beginning of the description
wherein, according to the invention, the processing means include a
further limiter circuit, adapted to receive the output signal of
the first limiter circuit and carry out limitations regarding even
variations in the opposite direction to the pre-established
direction, the resultant signal being utilized to obtain the
measurement signal, the apparatus also including control means to
enable and inhibit the further limiter circuit.
The invention is now described with reference to the accompanying
drawings given by way of non-limiting example, wherein same parts
or equivalent ones are marked with the same reference numbers and
in which:
FIG. 1 is a block diagram according to a first embodiment of the
invention, referred to a single feeler gauge mounted on a surface
grinding machine with a rotary table;
FIG. 2 is a more detailed circuit diagram of a circuit of the gauge
of FIG. 1;
FIG. 3 shows possible signal wave forms to illustrate the operation
of the gauge of FIGS. 1 and 2;
FIG. 4 is a block diagram illustrating a variant of the electric
circuits of the gauge of FIG. 1, according to a preferred
embodiment of the invention; and
FIG. 5 illustrates possible signal wave forms of the gauge of FIG.
4.
With reference to FIG. 1, the workpieces 11 arranged on rotary
table 12 of a surface grinding machine are successively contacted
by feeler 14 of a measuring head 15 supported by a support 17
mounted on the grinding machine. Head 15 houses a position
transducer, not shown, the output signal of which is responsive to
the position of a movable element of the transducer. The movable
element is carried by an arm (not shown) carrying feeler 14. The
transducer output signal reaches an amplifier-detector 18 whose
output is connected, by means of a resistor 20 of R.sub.1 value, to
a limited decrease-rate circuit 22, downstream of which there are a
low pass filter circuit 23 and a processing and indication unit
24.
A comparator circuit 25 receives at the positive input the output
signal of the amplifier-detector 18 and at the negative input the
output signal of the low-pass filter 23.
A relay 29 includes a coil 27, the energizing of which is
controlled by the output of comparator 25, a contact 30 arranged in
a connection between the output of filter 23 and through a resistor
32, of R.sub.2 value, the input of the limited decrease-rate
circuit 22, and another contact, indicated in FIG. 2 by reference
number 34, displaced together with contact 30 by means of the
functional connection 35 and adapted to control the limited
decrease-rate circuit 22.
Naturally, relay 29 can be advantageously replaced by electronic
switches.
With reference to FIG. 2, the limited decrease-rate circuit 22
includes an amplifier 37 with an input connected to resistor 20 and
a diode 38 that has the anode connected to the output of amplifier
37 and the cathode connected to an input of another amplifier
40.
Connected to the cathode of diode 38 are also a resistor 42 which
has a terminal biased by a source of negative voltage, a capacitor
45 having a terminal grounded and a contact 34 in series with
another resistor 43 which has a terminal biased by the source of
negative voltage.
The output of amplifier 40 is connected to the second input of the
same amplifier and with the second input of amplifier 37. Upon
examining the figure, it is evident that capacitor 45's voltage
follows the positive variations of the input signal of circuit 22
whereas the decreasing voltage speed is limited by the time
constant due to resistor 42 or to that due to resistors 42, 43 when
they are connected in parallel.
Now follows an explanation of the apparatus shown in FIGS. 1, 2,
with reference to FIG. 3 wherein the wave form indicated by letter
"a" shows a possible time diagram of the output signal of
amplifier-detector 18, the wave form marked by letter "b" shows the
corresponding output signal of limited decrease-rate circuit 22 and
the wave form marked by letter "c" indicates the output signal of
filter 23.
The curve "a" directly represents the movement of the movable
element of transducer of head 15, in particular the movement due to
the fast fall of the feeler 14 in the gap between a workpiece 11
and the following one, until reaching the stroke limit stop, the
movement due to the subsequent contact of the feeler with the
following workpiece, with increasing of the signal and positive and
negative overshoots with respect to the amount relative to the
upper surface of the workpiece, due to the sudden impact which
causes feeler 14 to bounce and the arm supporting the latter to
bend.
By examining curve "b" it is possible to realize that in the phase
when feeler 14 is falling into a gap, the limited decrease-rate
circuit 22 reduces the signal variation speed to a value determined
by the circuit itself. Basically this value is determined by the
time constant of discharge, through resistor 42, of capacitor 45 in
FIG. 2 and it is pre-chosen by considering the theoretical removal
rate of stock from workpieces 11.
When feeler 14 touches the following workpiece 11, the output
signal of amplifier-detector 18 increases until it exceeds the
output signal of filter 23 (curve "c").
Comparator 25, which receives the difference between the two
signals, switches over when said difference takes a positive value,
causing relay 29 to energize. Contact 30 closes and activates a
feedback loop between the output of filter 23 and the input of
limited decrease-rate circuit 22.
The closure of this feedback loop prevents the overshoots of the
detector amplifier 18 signal--said overshoots ensuing from the
sudden contact of feeler 14 with the workpiece surface and from the
relevant transient--from being directly applied to the input of the
limited decrease-rate circuit 22, and through the latter, to filter
23. In fact, as it may be seen by curve b, these overhsoots are
attenuated according to the ratio
this ratio is chosen so as to conveniently attenuate the
overshoots, but at the same time allow filter 23 to update its
output to the level of the signal corresponding to the workpiece 11
dimensions.
Measurement updating is facilitated by the fact that, while relay
29 is energized, contact 34 is closed and it keeps resistor 43 in
parallel to resistor 42 so considerably reducing the discharge time
constant of capacitor 45.
When relay 29 deenergizes, contacts 30, 34 open and the decrease
speed of curve b is again limited by the limited decrease-rate
circuit 22.
In this way it is possible to obtain a signal (curve c) at the
output of filter 23 which represents with considerable accuracy the
height dimension of workpieces 11, a dimension which decreases
during machining due to the removal of stock.
In the apparatus shown in FIG. 4, the output of low pass filter 23
is connected to an input of a summing circuit 47 which receives at
another input 48 a pre-determined reference signal.
The output of the summing circuit 47 can be connected, by means of
a contact 50, to the input of the limited decrease-rate circuit
22.
The output of the low pass filter 23 is also connected to the
negative input of a comparator 51 which receives at the positive
input the amplifier-detector 18 signal. The output of the
comparator 51 is connected to winding 54 of a relay 55 which
operates contact 34 (FIG. 2) of the limited decrease-rate circuit
22.
Another comparator 57 has a positive input connected to the
amplifier-detector 18 and a negative input connected to the output
of the summing circuit 47. The output of comparator 57 is connected
to the winding 60 of a relay 62 which operates contact 50.
The operation of the apparatus of FIG. 4 is easily understood with
the aid of FIG. 5, wherein the curves, a, b, c, have an analogue
meaning to that described for FIG. 3.
In correspondence with the overshoots of curve "a" with respect to
the sum of the ordinates of curve "c" and of the reference signal
previously mentioned, the contact 50 is closed and the level of the
output signal of the limited decrease-rate circuit 22 is limited,
because at the input of the same circuit arrives the sum of the
output signal of filter 23 and of the fixed increment corresponding
to the reference signal set in summing circuit 47.
Moreover, when the value of the output signal of filter 23 is
greater than the value of output signal of amplifier-detector 18,
the limited decrease-rate circuit 22 is inhibited by the closure of
contact 34, facilitating the updating of the same circuit 22 output
signal with respect to the amplifier-detector 18 output signal.
The apparatus shown in FIG. 4 can be simplified by eliminating the
comparator 51 and relay 55 and by controlling contact 34, as well
as contact 50, by relay 62.
It is also possible to eliminate comparator 57 and make relay 55
control contact 50, and also contact 34.
In consideration of the mechanical characteristics of the gauges
(in particular the acceleration during the free fall of the
feelers), it is possible to choose for the apparatuses shown in
FIGS. 1 and 4, the values of slope and level limitations of the
signals in order to cover an extremely broad range of applications,
without necessitating any adjustments. It is evident that the
invention can be applied to gauges including one or two feelers,
with or without hydraulic dampers operating on the movable
arms.
It is also obvious that if the polarities of the signals are
opposite with respect to those described, for circuitry design, or
owing to particular applications, instead of a limited
decrease-rate circuit, a limited increase-rate circuit is used and
the level limitation is made in a corresponding way.
Moreover, instead of a level limitation, it is possible to carry
out a speed limitation for variations in the opposite direction to
the one in which the first limiter circuit 22 intervenes. In this
circumstance it is possible to utilize a single slope limiting
circuit, having disconnectable components.
Obviously, the aforedescribed embodiments can undergo other
variants and changes equivalent from a functional and structural
point of view without falling outside the scope of the present
invention.
* * * * *